As a driving/electric-power generating system using a conventional vehicle AC generator, there has been known one in which has a three-phase winding and a three-phase inverter as described in, for example, Japanese Patent Laid-Open No. 2004-7964.
In the driving/electric-power generating system for vehicle described in Japanese Patent Laid-Open No. 2004-7964, however, since the application of the three-phase inverter is considered for a vehicle AC generator having one three-phase winding, the three-phase inverter cannot drive a vehicle AC generator having plural set of independent three-phase windings. In the application of the three-phase inverter to the vehicle AC generator having two set of independent three-phase windings, for example in case of using the vehicle AC generator as an actuator (motor for driving), if assuming that in-phase windings having a phase difference in the two independent three-phase windings are connected to each other without particular considerations at driving, circulating currents flow in in-phase windings because the in-phase windings have the phase difference, thereby causing an increase in the amount of heat generated.
Also, since the vehicle AC generator becomes a three-phase generator at the generation of electric power, a ripple voltage of a rectified voltage increases. Further since a circulating current flows even at the power generation where an electrical phase difference exists between the in-phase coils, a generated current decreases. Accordingly, such a driving/electric power generating system is accompanied by the problem that noise increases as well as a reduction in the efficiency of power generation, and a reduction in efficiency due to an increase in the amount of generated heat is incurred.
An object of the present invention is to provide a driving/electric-power generating system for vehicle which can reduce the amount of heat generated at driving to improve drive efficiency and can increase the efficiency of generation of electric power.